Floating connection



May 19, 1953 H. LEONARD, ,IR

NLOATING CONNECTION Filed March 4, 1952 N w @m 1.

INVENTOR ,Byron H. Leonard, Jr. BMJ

ATTORNEY Patented May 19, 1953 2,639,172 FLOATING .CONNECTION Byron H.Leonard, Jr., St. Louis, Mo., assigner to the United States of Americaas represented by the Secretary of the Interior Application March4,1952, Serial No. 274,819

8 Claims. (Cl. 287 -85) (Granted undermine a5, U. s. code (1952),

sec. 266) The. invention herein described and claimed -may bemanufactured and used by or for the Government of the United States ofAmerica for governmental purposes without the payment of royaltiesthereon or therefor. y

.This invention relates to an improved oating I*joint for connecting apair of separately guided "reciprocating members, such as a crossheadand a plunger.

It is often desirable to provide a floating connection, rather than arigid one, between two separately guided members, one of which isVdriven bythe other in rectilinear reciprocation along substantially thesame axis. In such an arrangement, because of machining difficulties,v

or required running tolerances, it is usually extremely difcult, orimpossible, to maintain perfect alignment of the axes of the separateguides. Both angularity (the aires of the separate guides are askew toone another) and offset (the axes of the separate guides are parallel,but laterally oiset from one another) are encountered. For example, inhigh pressure equipment employing reciprocating plungers, such as inhigh pressure pumps, wherein the plunger is usually connected to thedriver by means of a guided crosshead or yoke, it is essential that theplunger run absolutely true through the packing with very closeclearances in order to effect a seal. Sidewise thrust on the plungerbecause of angularity or offset between the crosshead guides and thebore of the plunger would soon damage the packing and cause leakage.with such an arrangement, the running clearance needed between thecrossv.head or yoke and its guide must be considerably larger than thatwhich can be tolerated through the packing. Even if these toleranceswere not considered, veryl` accurate machining would be required toprevent angularity and offset between the axes of the plunger bore andthe guides. To remedy this, a iieiiible joint is sometimes empose havebeen previously proposed, but these joints `are usually of a purelymechanical type,

.permitting ra certain amount of sliding play between the elements.Becausevsliding friction is involved, these joints are often undulystiff. Furthermore, many of these prior connections permit only lateralplay, thus Afor offset, and not angularity, between the axescompensating only of thereciprocatlng members. y The principal object ofthis invention is to provide a floating connection between twoseparately guided reciprocating members which is free from 'mechanicalfriction, and which compensates'for both angularity and offset betweenthe axes of the separate guides. Other objects of the invention will beapparent from the description which follows.

Broadly, the invention is characterized by the fact that the forceexerted by the driving .member is transmitted to the driven memberthrough a fluid cushion. The fluid is contained uin a chamber carriedyby one of the reciprocating members. A plug, carried at the end of theother reciprocating member fits into the open end of the chamber, andoccupies a portion of its volume. The plug is so dimensioned as tooccupy the greater portion o the open end of the chamber, leaving asmall clearance between its periphery and the adjacent walls of thechamber. vA clearance is likewise provided between ythe bottom side ofthe plug and the bottom of the chamber. A iiexible sealing means isconnected across the periphery of the plug and the adjacent walls of thechamber so as to close the gap between the two, and to seal the duidinthe chamber. With this arrangement, the force exerted by the drivingmember during its forward stroke is transmitted to the driven memberthrough the fluid contained in the chamber. By virtue of the iiexibilityci the sealing means connecting the plug to the chamber, and because ofthe clearances between the periphery of the plug and the adjacent wallsof. the chamber, and between the `bottom of plug and the bottom ofthechamber, the plug (and consequently the member to which it is attached)is permitted to move relatively of the driving member in all directionsin an amount suiicient to compensatefor both angularity and offsetbetween the separate guides for the two reciprocating members. i i

For a better understanding of the invention, and for a fullerdescription thereof, reference-is now made to the accompanying drawingwhich illustrates its use in a high pressure pump.

The single figure is a view, partly in section. showing the crossheadand plunger assembly and the floating joint connecting the two.

In the drawings, the reference numeral I refers to a steel yoke whichsupports, in proper alignment, the crosshead guides 2 and the pumpcylinder 3. The crossheadl 4, sliding in the take care of angular-itybetween the 3 n guides 2, is driven by drive rod by suitable means, notshown. The pump plunger 8 is driven by the crosshead 4, and runs in abore provided with a suitable packing 1.

A cylindrical recess is provided in the forward end ofthe crosshead.This recess forms a chamber 8, having an open end facing the plunger 6.A cylindrical plug 9, fastened to the end of the plunger 6, fits intothe open end of the chamber 8, occupying a portion of its volume. As maybe seen, the plug 9 occupies the greater portion of the open end of thechamber, leaving only a relatively small clearance between the peripheryIll of the plug and the adjacent walls I I of the chamber. It willlikewise be noted that the plug is so arranged in the chamber that aclearance is left between the bottom I2 of the plug and the bottom I3 ofthe chamber. For the sake of clarity of illustration, the clearancebetween the periphery of the plug and the side walls of chamber 8, andbetween the bottom of the plug land the bottom of the chamber, have beenexaggerated. Actually, in ordinary applications, these clearances -needbe of the order of a quarter of an inch, since ordinarily the amount ofangularity and offset encountered will not require larger clearances.

-It is particularly desirable to maintain relatively small clearancesbetween the periphery of the plug and the side walls of the chambersince, in

this way, the area of the flexible diaphragm or other flexible sealingmeans closing the gap therebetween, is kept small, and consequently thetotal pressure exerted by the fluid in the chamber on 1 the diaphragmduring the pressure stroke of the plunger is kept correspondingly small.

A flexible diaphragm I4, which is preferably of the bellows-type, asillustrated in the drawing, is connected across the gap between theperiphery of the plug and the adjacent walls of the chamber. As can beseen, the annular, bellows-type diaphragm I4 is connected, by weldingfor example, to a pair of annular supports I6 and I5, which are bolted,or otherwise attached to the plug 9 and tothe crosshead 4, respectively.The diaphragm may be constructed of any suitable strong, flexiblematerial such as light gauge steel, neoprene; the strength requireddepends on the magnitude of the fluid force developed in cavity 8.

The Vportion of the chamber 8 not occupied by the plug 9 is completelyfilled with a fluid of suitable characteristics. A liquid such as brakefluid, or other type of fluid usually vemployed in hydraulic systems, ismost suitable. A gas under high pressure could also be used. Ports, suchas port Il, are provided for introducing the fluid into chamber 8.

It will be apparent that, during the forward or pressure stroke, theforce exerted by the crosshead is transmitted through the fluid inchamber 8 to plug 9, carried by the plunger. Sufllcient clear-ance ispermitted between the periphery of the plug 9 and the adjacent walls ofthe chamber, and between the bottom of the plug and the bottom of thechamber, to allow for any angularity and offset which is likely to occurbetween the 'crosshead guides and the bore of the plunger. With thisarrangement, it is apparent that the plunger will-always run truethrough the Dacking; being freely guided by the packing unit aloneirrespective of such angularity and offset. As shown in the drawing, therear edges of the plug are preferably beveled as at I8 to permit greaterfreedom of movement of the plug in tilting to crosshead guides and'theplunger' bore. f

lso

Since, on the return stroke, the flexible dlaphragm I4 is the onlyconnecting link between the plunger and the crosshead it will bedesirable to provide auxiliary means, which are inoperative on theforward stroke, to remove the strain on the diaphragm on the returnstroke. Thus, if the diaphragm I4 is not sturdy enough to overcomepacking friction and the inertial forces involved, rigid connections maybe provided, such as the U-shaped member I9. As may be seen in thedrawing, the member I9 is fastened to the crosshead and is so arrangedthat it bears upon the plug 9 only during the return stroke, thusrelieving the strain upon the diaphragm, and preventing its rupture.Preferably, three or more of the supports I9 are employed, spaced aroundthe circumference of the chamber, or instead, an annular U-shaped membercould extend around the entire circumference of the chamber forming acontinuous support.

According to the preferred embodiment of the invention, the diameter ofthe plug 9 is considerably larger than the bore in which the plungerworks. This has the effect of reducing the pressure developed in thefluid in chamber 8 during the forward or pressure stroke. For example,if the plunger 6- were pressuring against a force of 10,000 lbs. per sq.in., and the ratio of the diameter of a plunger bore to the diameter ofthe plug 9 was 1:10, the pressure developed in the fluid in the chamber8 would be only 1,000 lbs. per sq. in. This is an important feature,since the total pressure developed in the fluid in the chamber 8determines the necessary wall thickness of the diaphragm I4 and the wallthickness determines the flexibility of the diaphragm. The more flexiblethe diaphragm, of course, the greater freedom of movement which ispermitted to the plunger 6 in aligning itself with its bore.

It is to be understood of course, that the in- -vention has applicationsother than that described above and that many modifications of thestructure shown are possible within the scope of the invention.Consequently, the invention is not to be limited by the specificembodiment illustrated, but only by the scope of the appended claims.

I claim:

l. In a device comprising two connected members, one driven by theother, and each separately guided for rectilinear reciprocation alongsubstantially the same axis, whereby slight angularity and offset islikely to occur between the axes of the separate guides, an improvedfloating connection between saidV members including a chamber having anopen end carried by one of said members, a plug carried by the other ofsaid members fitting into the open end of said chamber and occupying aportion of its volume, said plug being dimensioned so as to occupy thegreater portion of lthe open end of said chamber,

leaving a small clearance between its periphery and the adjacent wallsof said chamber, said plug likewise being arranged so as to leave aclearance between its bottom side and the bottom of.' said chamber,flexible sealing means vconnected across the periphery of said plug andthe adjacent walls of said chamber so as to close the gap therebetween,the remaining portion of said chamber unoccupied by said plug being lledwith a. fluid, whereby the force exerted by said driving member istransmitted to said driven member through said fluid, thereby permittingautomatic compensation for bothangularity and oflsetbetween'th -axesof'said separate guides.

2. A device in accordance with claim 1 in which said flexible sealingmeans is a bellows-type diaphragm.

3. A device in accordance with claim 1 which is provided with means,inoperative on the forward stroke of the driving member, for supportingsaid plug on the return stroke, and thereby preventing rupture of saidflexible sealing means.

4. In a device comprising two connected members, one driven by theother, and each separately guided flor rectilinear reciprocation alongsubstantially the same axis, whereby slight angularity and offset islikely to occur between the axes of the separate guides, an improvedfloating connection between said members including a recess in one of'said members forming a chamber therein yhaving an open end facing towardthe other ofksaid members, a plug carried by the other of said membersfitting into the open end of said chamber and occupying a portion of itsvolume, said plug being dimensioned so as to occupy the greater portionof the open end of said chamber, leaving a small clearance between itsperiphery and the adjacent walls of said chamber, said plug likewisebeing arranged so as to leave a clearance between its bottom side andthe bottom of said chamber, a flexible diaphragm connected across theperiphery of said plug and the adjacent walls of said chamber so as toclose the gap therebetween, the remaining portion of said chamberunoccupied by said plug being filled with a fluid, whereby the forceexerted by said driving member is transmitted to said driven memberthrough said fluid, thereby permitting automatic compensation forangularity and offset between the axes of said separate guides.

5. In a device comprising a reciprocating, separately guided drivingmember, connected to a plunger working in a bore having substantiallythe same axis as the guide for said driving member, whereby slightangularity and offset is likely to occur between the axis of said guideand the axis of said bore, an improved floating connection between saiddriving member and said plunger including a chamber having an open endcarried by said driving member, a plug carried at the end of saidplunger fitting into the open end of said chamber and occupying aportion of its volume, said plug being dimensioned so as to occupy thegreater portion of the open end of said chamber, leaving a smallclearance between its periphery and the adjacent walls of said chamber,said plug likewise being arranged so as to leave a. clearance betweenits bottom side and the bottom of said chamber, a flexible diaphragmconnected across the periphery of said plug and the adjacent walls ofsaid chamber so as to close the gap therebetween, the remaining portionof said chamber unoccupied by said plug being filled with a fluid,whereby the force exerted by said driving member is transmitted to saidplunger through said fluid, the clearance between the periphery of saidplug and the adjacent walls of said chamber, and the clearance betweenthe bottom of said plug and the bottom of said chamber, being sufficientto permit said plug to move relatively of said chamber in all directionsin an amount sufficient to compensate for both angularity and offsetbetween the respective axes of said guide Iand said bore.

6. A device in accordance with claim 5 in which the diameter of' saidplug is substantially greater than the diameter of said bore so asl-"tosubstantially reduce the pressure developed in said fluid during thepressure stroke of said plunger.

7. A device constructed in accordance with claim 5 which is providedwith meansfv inoperative on the forward stroke of said driving means,for supporting said plug on the return f stroke, and thereby preventingrupture of said flexible diaphragm.

8. In a device comprising a reciprocating, sep- `arately guided drivingmember connected to a y said plug being dimensioned so as to occupy thegreater portion of the open end of said chamber,

leaving a small clearance between its periphery and the adjacent wallsof said chamber, said plug likewise being arranged so as to leave aclearance between its bottom side and the bottom of said chamber, aflexible bellows-type diaphragm connected across the periphery ofsaidplugr and the adjacent walls of said chamber so as t'o close the gaptherebetween, the remaining portion of said chamber unoccupied by saidplug being filled with -a fluid, whereby the force exerted by saiddriving member is transmitted to said plunger through said fluid, theclearance between the periphery of said plug and the adjacent walls ofsaid chamber, and the clearance between the bottom of said plug and thebottom of said chamber, being sufficient to permit said plug to moverelatively of said chamber in all directions in an amount sufficient tocompensate for both angularity and oil'- set between the respective axesof said guide and y said plunger, the diameter of said plug beingsubstantially greater than the diameter'bf 'fsaid bore so that thepressure developed in saidfluid during the pressure stroke of saidplunger isr substantially reduced. j

BYRON H. LEONARD, JR.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,560,492 Powell Nov. 3, 1925 1,642,211 Langdon Sept. 13, 19271,909,768 Jones May 16, 1933

